Brad Shaffer

Ecology, Evolution, Conservation ScienceLos Angeles

California
is prey to a multitude of disaster scenarios, both real and imagined. In his 1999 book “Ecology of Fear,” historian Mike Davis catalogued the
state’s dance with destruction, noting that the city of Los Angeles alone has
been destroyed no less than 138 times in novels and films since 1909.

The
reality of environmental damage is often slow and subtle, the death of a
landscape by a million cuts. That’s where the waterdog comes in.

The
story starts in the 1950s when a couple of enterprising bait dealers from the
Salinas Valley retrofitted the bed of a pickup truck with a mini-swimming pool
and headed off to Texas and New Mexico for a salamander roundup. Not just any salamander: California’s native
tiger salamanders produced larvae that grew only about 5 inches long, but
the larvae from the barred tiger salamanders found in Texas and New Mexico were
twice that size. The waterdogs, as they were nicknamed, produced twice as much bait for the buck.

Today,
the introduced barred tiger salamander is helping to push the California tiger
salamander toward extinction, according to UCLA professor and amphibian expert
Brad Shaffer. There are many reasons the native salamander is in trouble, but
one of the most intriguing is that the two species interbreed, and the hybrid
salamanders energetically outcompete the natives.

This
is bad news for the California’s native landscape, but fascinating for
scientists, especially since analysis of gene mapping by the Max Planck
Institute for Evolutionary Anthropology in Leipzig, Germany, reveals that human
evolution went through much the same process. Just recently, the New York Times
ran an article about research showing that early humans and Neanderthals
interbred more than 40,000 years ago, and natural selection favored the hybrids
with improved genetic immunity to disease. Thanks to Shaffer’s research at UC Natural Reserve System sites, we now have a chance to see that process in real time, not in
humans, but in the endangered tiger salamander.

You recently left UC Davis after 25 years. What did you leave behind, in terms of the work you do?

Answer:

We run a project at the
Jepson Prairie Preserve in the Sacramento Valley, one of the UC Natural Reserve
System sites. Our study is a very detailed, 10-year study of the California
tiger salamander, which is an endangered species. We’re in year nine.

Question:

So the location was important.

Answer:

This study really leverages the Natural Reserve System because it
utilizes the vernal pool the salamanders breed in. Vernal pools are ephemeral,
and increasingly rare in California. The vernal pool at Jepson, Olcott Lake,
may be the largest vernal pool left in the Central Valley. It’s enormous, about
80 acres when it fills up.

Question:

So researchers have to run out to Jepson whenever it rains?

Answer:

That’s not the only challenge when it comes to this salamander. They
spend all but a handful of the days and nights of the year underground in
gopher burrows, so you don’t know where they are. When it rains, they march up
to ponds and breed and march back down again. It’s really a trick to find out
where they are and how much land you need to protect to keep a healthy population
of salamanders.

Question:

We were wondering if you were conflicted about the threat posed by interbreeding with the introduced species, because scientifically, it's very interesting, yet it's a significant threat to the native species, as well.

Answer:

That’s exactly right. The
story fascinated me. In the 1920s, 1930s and 1940s, essentially all the rivers
in California were dammed and all these fish from the eastern U.S. were
introduced, creating a sportfishing industry that is 100 percent based on
non-native fishes in reservoirs and non-natural bodies of water.

California tiger
salamanders had larvae and those larvae were used as bait, but the California
salamanders metamorphose and turn into the terrestrial form when they’re only
about 5 inches long, while salamanders from other places get huge, a foot long.

Question:

So it was obvious to use those non-native salamanders?

Answer:

Fifty years ago, yes. I
actually found one of the guys who transplanted the non-natives from Texas and
New Mexico. Took him out to lunch, we chatted about it. He wasn’t doing
anything illegal at the time.

Question:

What's the science interest?

Answer:

This hybridization
phenomenon is fascinating. You take two species; they’ve been separated for 5
million years. Do a massive transplantation experiment and see what happens. Today,
after 50 or 60 years, we have the ability to look at individual genes and the
genome, and see if there are parts of the native genome that outperform the
non-native one and vice versa.

Question:

Are we learning anything new about speciation from the unfortunate-sounding marriage?

Answer:

One of the fascinating
things from a scientific perspective is that it’s really in its early stages. We’re
talking about 20 or 30 generations of salamanders. Some of the genes that are
coming in from the non-native species are extraordinarily favored by natural
selection. Within a couple of generations they replace the native genes. I
never would have predicted that, because the California tiger salamanders
evolved here. Why in the world would these non-native genes be so much more
fit?

We have 68 genes that
we’ve studied closely. Three of the non-natives trounce the native genes. They
take over more quickly and they move more rapidly across the landscape, and the
three genes together act as a unit. We have evidence suggesting that if a
salamander has these non-native genes, they grow more quickly, they
metamorphose at a much bigger size, and that probably means they can walk
faster and move across the landscape more quickly.

Question:

A salamander super race?

Answer:

Exactly. The only reason
we can understand it in this case is that we’re watching it happen in real
time. If these genes had spread across the native species you’d just think it
was something that evolved here, in the native species. You need pure populations
to compare to the hybrid. This hybridization event is very recent, but it’s old
enough so that these dynamics are happening.

Question:

Great science, but not so great for the salamander.

Answer:

We’re working closely
with the U.S. Fish and Wildlife Service and the California Department of Fish
and Game to find ways to incentivize landowners to modify their land to favor
the native salamander. From a conservation point of view it’s a horrible
problem, but from a biological point of view it’s fascinating. We’ve invested a
lot in studying it from both points of view.